1. Field of the Invention
The present invention relates to a cylindrical vibration damping apparatus favorable for use as an automotive engine mount or torque roll mount, for example, and more particular to a cylindrical vibration damping apparatus equipped with a rubber stop plate constituting a stopper mechanism in the axial direction.
2. Description of the Related Art
As one type of vibration damping apparatus known in the art for installation between parts that make up a vibration transmitting system, there is known a cylindrical vibration damping apparatus comprising a vibration damping unit of cylindrical shape, having a metallic outer cylindrical member disposed spaced apart to the outside of a metallic inner shaft member, with the inner shaft member and the outer cylindrical member being connected by means of a rubber elastic body. Cylindrical vibration damping apparatus of this kind are used, for example, as automotive engine mounts or torque roll mounts.
Cylindrical vibration damping apparatus of this kind are often equipped with a stopper mechanism in the axial direction, for cushion-wise restriction of relative axial displacement of the inner shaft member and the outer cylindrical member when large load is input in the axial direction. Such an axial stopper mechanism may be realized in the manner taught in Citation 1 or Citation 2 for example, by installing a pair of rubber stop plates that spread out in the axis-perpendicular direction, disposed at the two axial ends of the inner shaft member in the cylindrical vibration damping unit. Specifically, with the cylindrical vibration damping apparatus mounted onto an automobile, the two axial end faces of the outer cylindrical member, with the rubber stop plates sandwiched between, are positioned in axial opposition to brackets or other contact members affixed to the axial ends of the inner shaft member, and the outer cylindrical member is placed in abutment via the rubber stop plates with the contact members affixed to the inner shaft member, whereby cushion-wise stopper functionality in the axial direction is achieved.
The rubber stop plate installed in such a cylindrical vibration damping unit typically has a generally flat plate shape, provided in the center portion thereof with a mount hole that fits about the outside of the inner shaft member. However, it does not necessarily have the simple flat disk-shaped rotating body shape taught in the aforementioned Citations 1 and 2. Specifically, as taught in Citaton 3, in many instances, due to considerations such as for reasons of interference with brackets or other components or installation space, or of the extent of relative displacement of the inner shaft member and the outer cylindrical member in the axis-perpendicular direction produced by loaded weight exerted on them in the installed state, the rubber stop plate is given varying diameter dimension in the circumferential direction around the inner shaft member. Also, in many instances a rubber stop plate is designed such that one face thereof is supported superposed hermetically over the entire face thereof against the bracket or other contact fitting, while the other face thereof has formed thereon an elastic projection that projects in an appropriate size and shape, thereby providing stable support while at the same time adjusting the cushioning function at the time of contact so as to achieve non-linear spring characteristics.
That is, with rubber stop plates of this kind, during installation onto the cylindrical vibration damping unit, it is necessary to carry out the installation procedure in an error-free manner, while (1) not only identifying the correct position in the circumferential direction thereof, but also (2) identifying the front and back thereof. In the event of improper installation, it will be necessary after inspection to remove and then reinstall the rubber stop plate. In view of recent deliberations regarding shipping components with the bracket attached, in the event that the rubber stop plate were found to be improperly installed during inspection after the bracket has been attached, it would be necessary to remove the bracket in order to perform the repair operation, resulting in the significant problem of a considerable amount of extra labor.
However, in the cylindrical vibration damping apparatus of conventional design taught in Citatons 1 and 2, there are employed no arrangements that require identifying either the circumferential position or the front from the back of the rubber stop plate during installation. With the cylindrical vibration damping apparatus of conventional design taught in Citaton 3, in order to be able to identify the installation position of the rubber stop plate, a single indented mating portion is formed at one location along the circumference. However, it is not possible thereby to distinguish the front and back of the rubber stop plate, so that there remains a likelihood of drawbacks stemming from improper installation.
[Citation 1] JP-A-2000-205323
[Citation 2] JP-A-5-118367
[Citation 3] JP-A-11-125289